public class yb {
    class Solution {
        public boolean isUnique(String astr) {
            int t = 0;
            for(int i =0 ;i<astr.length();i++){
                int x = astr.charAt(i)-'a';
                if(((t>>x)&1)==1){
                    return false;
                }
                t |= 1<<x;
            }
            return true;
        }
    }
}
